The switches are kind of 'beta-features' that turn on different things that are not yet fully implemented in Star-CD. You normally don't need them to use subroutines, I think there is only one exception when you want to use a subroutine for a turbulence model. For all the other subroutines you have to choose "user" out of the possible choices and write the necessary code via "user-subroutines" in the Star menu to the subdirectory "./ufile".